Over the years, many label structures have been used and attached to various cartons, packages and the like. In this regard, different label structures have been utilized to conform with various needs and packaging requirements. An example of a somewhat specialized label structure is shown in U.S. Pat. No. 4,264,657, which issued to H. B. Tollette on Apr. 28, 1981. In particular, the Tollette structure included a foam layer, an intermediate printed layer, and a clear plastic film top layer. The foam layer of the Tollette label was designed to serve as a cushion to protect the labeled container from shocks and impacts experienced during shipping and handling, and the outer printed layer was to comprise a printed paper layer. The Tollette label structure was contemplated for use on glass containers which commonly were to be subjected to glass-to-glass packaging.
Another label structure designed for a particular and somewhat specialized application is shown in U.S. Pat. No. 4,528,055, which issued to J. C. Hattemer on July 9, 1985. In particular, the Hattemer patent concerns a label which can include a removable central coupon area which is detachable from the balance of the label and serves as a redemption, discount or promotional coupon for the product. The Hattemer label includes a pressure- sensitive paper base sheet, a paper top sheet, and a clear barrier sheet therebetween. These three layers are laminated together such that the top sheet can be removed while the clear barrier sheet remains attached to the base layer. The barrier layer prevents ink and other graphic printing from the top sheet to transfer to the base sheet.
Another multilayered label structure is shown in U.S. Pat. No. 4,581,262, which issued to J. A. Karabedian on Apr. 8, 1986. The Karabedian sleeve label is a coextruded multilayer sheet comprising a lower foam layer to be situated on the inside of the sleeve next to the container, and an outside printable solid skin layer made of a blend of high density polyethylene, block copolymer of styrene and butadiene, and polystyrene. Similarly, the brittle foam layer is to be a polystyrene material, and the foam and skin layers are bonded together such that the sheer bond strength therebetween is less than the yield strength of the tough outer skin, whereby when sheer stress is applied to the label laminate, the foam layer tears slightly away from the skin layer and the skin resists tearing. The label is contemplated to be heat shrunk onto the outside of a container and attached to such container only at limited points to facilitate easy removal of such label for recycling of the container. A similar label structure including the brittle foam layer and the outer tough skin is illustrated in U.S. Pat. No. 4,567,681, which issued to G. J. Fumei on Feb. 4, 1986. The Fumei plastic label includes a polystyrene foam layer which provides a solvent-soluble label portion whereby the plastic label can be wrapped around the container and attached to itself and the container only at predetermined finite areas. This limited attachment enables the easy removal of the label for recycling of the container.
Paper and paper-like labels having also been used in the in-mold labeling context in the formation of blow-molded containers. In this regard, it has been found that it is advantageous to place the paper label within the blow-molding mold prior to the expansion of a heated preform, whereby the paper label is integrally attached to the outer surface of the blow-molded container during such blow-molding procedures. An example of a transfer device for applying labels to blow-molds is shown in U.S. Pat. No. 4,359,314, which issued to E. W. Hellmer on Nov. 16, 1982. As explained in the Hellmer patent, the transfer device picks up a label from a stack of labels and moves the label into alignment with a pre-selected portion of the inner surfaces of a female mold cavity prior to blow-molding. Thereafter, a container preform is blown against the inner walls of the closed mold cavity and the label is adhered to the outer surface of such stretched pre-form.
While in-mold labeling procedures, such as described in the Hellmer reference, have certainly helped improve the economics, performance and appearance of labels on blow-molded thermoplastic containers, it has been found that conventional label stock materials often wrinkle, delaminate, or otherwise deteriorate under the thermal and mechanical stresses imposed thereon by the in-mold labeling procedures. In particular, the high heat inherent in in-mold labeling, and the subsequent shrinkage of the blow-molded thermoplastic material as it cools impose relatively severe stresses upon conventional label stock material, often causing the label to wrinkle, bubble, delaminate from the container and/or other layers of the label, or otherwise experience deterioration in its graphics or general appearance. Such deterioration and poor performance can become especially acute if the container is exposed to squeezing and/or a moist or wet environment. Despite the growing use of in-mold labeling in the industry, there remain problems in maintaining a smooth label surface and in maintaining the bonds of lamination between the label and the container and the various label laminated layers. Prior art label stock did not adequately provide solutions to these problems.